The present invention relates to a novel needle guide assembly which permits the needle guide outer cannula to function as a localizing needle and as a guide wire for placement of a surgical instrument or catheter at or within the target area to be examined.
The use of a small needle system (21-23 gauge) for placement of percutaneous nephrostomy tubes, abscess drainages, biliary endoprotheses, translumbar aortography or normal structure such as the kidney or an artery have become routine in the past several years because the small gauge needle can pass through most of the human anatomy without significant damage to the anatomy. However, a needle of this size is too small to permit adequate drainage for therapeutic purposes and it is too small to extract samples of infected material or suspect structure for diagnostic purposes.
Thus, the capturing of cells through such a small needle is, at times, wholly inadequate for a definitive diagnosis. In 1979, a new system was introduced in which a long fine needle was used to localize the target. Subsequently, larger needles, catheters or other instruments were advanced over this needle into the target. Thus, larger samples could be obtained by the larger needle and catheters large enough for adequate drainage could be placed. In the average patient a 40 to 50 centimeter needle is required to place short drainage catheters and biopsy needles, and 50 to 200 centimeter needles are required to place longer angiographic catheters. This length is necessary because when the long fine needle is inserted into the body it is necessary that the needle have a length extending outwardly from the skin or surfaces of the anatomy which is greater than the length of the catheter drainage instrument biopsy needle that is going to be positioned over the fine needle for insertion into the body tissue or target area. Because of the occasionally extreme length of such a needle system, it has been suggested that a 21-22 gauge fine needle be utilized to localize or penetrate a particular organ or target. A shorter outer needle or catheter is inserted over this needle into the target. The inner fine needle is removed and a standard guide wire is advanced through the larger needle as in the standard Seldinger technique (1954). During the several steps required to place the larger guide wire, there is a possibility of losing access to the target. Also the standard guide wire is flexible and not near as rigid as the original fine needle which was used for the initial search. If the fine (22 gauge) needle is used with a standard guide wire 0.018 inches (as the standard Seldinger technique), this inner wire is not strong enough to permit single step placement or larger biopsy needles or drainage catheters.
The present invention is directed to an assembly which overcomes these difficulties.